The present invention relates to a drive system particularly, but not solely, for use with mining apparatus and especially chain-driven mining apparatus.
Mining apparatus employing driven chains, such as coal ploughs or scraper-chain conveyors, usually require high performance drive means with electric or hydraulic motors and reduction gearing. It is common to provide safety devices such as shear pins to preclude damage in the case of abnormally high loads and to prevent breakage of the chain or chains. In the event of fracture of a shear pin the sudden release of loading may often cause a highly-tensioned chain to whip or spring-back with resultant danger to personnel. Usually the gearing needs to provide a transmission ratio in the order of 16:1 and a two stage gearing would be appropriate. However in order to accommodate the shear pin it has been necessary to provide an extra stage and the resultant three-stage gearing has meant a relatively large and heavy unit. Another requirement of the drive means is for the direction of drive to be reversible and for there to be some control of speed. The latter is particularly desirable with a plough. In certain circumstances it is often necessary to control the tension in the chain and hitherto a variety of special ancillary devices have been constructed for this purpose.
With regard to the foregoing a general object of this invention is to provide an improved form of drive system.